The invention seeks to provide a more efficient and economical method for coating a metal strip moving at high speed in a rolling mill or process line with oil or other lubricant. More particularly, the invention provides an improved ionic strip coating method which operates at a much lower and safer voltage and amperage than known prior art systems, lessens the consumption of oil and more completely and uniformly coats the metal strip on both sides during its passage through a very compact coating apparatus which requires much less floor space than prior art systems. The apparatus used to carry out the method is a unit which contains an electrical power supply, a circulating system for lubricant enabling excess lubricant to be recovered, and a pair of pinch rolls through which the lubricated strip may pass. The propose of the pinch rolls is only to hold a fixed pass line of the strip with respect to the oil discharge headers.
In accordance with an important feature which distinguishes the invention from the prior art, a pressurized gas, such as air, in the form of jets or sprays is directed at the attracted oil streams as they exit from a header and these streams are dispersed into a multitude of finer streams in a crossing pattern which assures complete and uniform coating of the moving strip across its full width.
Known prior art ionic systems operate at a voltage and current value far above that of the invention, and consequently are capable of causing a lethal shock. Prior art voltage and current are of the order of 150,000 volts at 1000 microamps. In contrast of this, the invention utilizes 60,000 to 100,000 V. at only about 10 microamps. As a consequence, the invention is entirely safe and cannot cause a lethal shock.
Additionally, from a construction standpoint, the apparatus employed in the method is much simpler and more compact than the prior art.
Other features and advantages of the invention will become apparent during the course of the following description.